A semiconductor device such as a switching device and a diode is used for a circuit such as a switching power source and an inverter. These semiconductor devices are required to have high breakdown voltage and low on-resistance. Further, a relation between the breakdown voltage and the on-resistance has a trade-off relation determined by a device material.
By the progress of technological development till today, low on-resistance of a semiconductor device nearly up to a limit of silicon has been realized. In order to further improve the breakdown voltage and further reduce the on-resistance, it is necessary to change the device material from silicon. By adopting a wide bandgap semiconductor such as GaN based semiconductor like GaN and AlGaN or Silicon Carbide (SiC) as the switching device material, the trade-off relation determined by the material can be improved and it is possible to dramatically raise the breakdown voltage and reduce the on-resistance.